1. Field of the Invention
The invention relates to the conversion of certain .gtoreq.C.sub.4 saturated acids, esters and aldehydes to the corresponding .alpha.,.beta.-unsaturated acids, esters and/or aldehydes by a gas phase oxydehydrogenation process.
2. Description of the Prior Art
The catalytic oxydehydrogenation of .gtoreq.C.sub.4 saturated acids, esters and aldehydes to the corresponding unsaturated acids, esters and/or aldehydes, in the gas phase, is known. The use of the catalysts employed for these reactions to date, however, has certain disadvantages. Halogens, such as iodine and bromine can be used in elemental, organic or inorganic form as catalysts for such reactions (U.S. Pat. Nos. 3,350,169; 3,356,750; 3,442,993; 3,466,149 and 3,770,812 and W. German OLS No. 2,064,576). Although these halogen catalysts provide relatively good results in terms of yields and efficiencies, these good results are seriously offset, from a commercial point of view by the relatively high cost of the catalyst, the difficulty in recovering the catalyst, and the highly corrosive nature of the catalyst.
The use of certain iron based contact catalysts has also been proposed, with and without the use of the halogen catalysts, for these reactions (U.S. Pat. Nos. 3,364,494; 3,855,279 and 3,917,673; U.K. Patent 1,250,749 and W. German OLS No. 2,438,464). In order to obtain relatively good results in terms of yields and efficiencies with these iron containing catalysts it is apparently necessary to conduct the reactions at relatively high temperatures and to use relatively large amounts of gaseous diluent such as nitrogen in the reaction stream.
The oxidation of various .gtoreq.C.sub.4 unsaturated aldehydes with oxygen to the corresponding unsaturated acid with various heavy metal catalysts is also known. (U.S. Pat. No. 3,833,649; W. German OLS Nos. 2,344,956 and OLS 2,511,076; Japanese Patent application publication Nos. J5-0670-318 and J5-0013-011).
Prior to the present invention, however, it has not been possible to readily oxydehydrogenate saturated .gtoreq.C.sub.4 acids, esters and aldehydes, in the gas phase at relatively low temperatures with relatively high levels of conversion, yield and efficiency to produce unsaturated compounds having the same numbers of carbon atoms.
The terms percent conversion, percent yield, and percent efficiency which are employed herein with respect to the present invention are defined as follows: EQU % conversion=Sf-Sr/Sf.times.100 I EQU % yield=P/Sf.times.100 II EQU % efficiency=P/Sf-Sr.times.100 III
wherein Sf=the moles of starting material fed to the reactor; Sr=moles of starting material recovered in effluent from the reactor; P=moles of product in effluent from the reactor.